1. Field of the Invention
The present invention relates to opening and closing mechanisms used in hinge joints of electronic devices adopting a folding design such as mobile phones.
2. Background Art
FIG. 6 is a sectional view of conventional opening and closing mechanism 30, and FIG. 7 is its exploded perspective view. Fixed member 31 has fixed cam 32 with sloped portions 32B and 32C.
Movable member 33 is disposed in a rotatable fashion and also axially-movable fashion relative to fixed member 31. Movable member 33 has a pair of movable cams 34 which engage with cam 32.
Fixed member 31, movable member 33, spring 36, and fixed shaft 37 are housed in cylindrical movable case 35 made of a metal sheet. Movable member 33 and movable case 35 are coupled via spring 36. Each of the tips of cams 34 is resiliently contacted against sloped portion 32B of cam 32 by the force of spring 36.
Fixed member 31 is secured to a left end of fixed shaft 37. Movable member 33 and movable case 35 are rotatably installed on fixed shaft 37. A right end of fixed shaft 37 protrudes outward from movable case 35. Ring-shaped stopper plate 38 made of metal is secured to the right end of fixed shaft 37 so as to retain movable case 35, configuring opening and closing mechanism 30.
This opening and closing mechanism 30 is, for example, employed in a hinge joint of a folding mobile phone as shown in FIG. 8. Though not illustrated in FIG. 8, opening and closing mechanism 30 acts as a hinge between fixed housing 42 and movable housing 43 by coupling fixed member 31 to fixed housing 42, and movable case 35 to movable housing 43, respectively.
In the above structure, a force in a closing direction is applied to movable member 33 when each of the tips of movable cams 34 is resiliently contacting sloped portion 32B of fixed cam 32, as shown in FIG. 6, and thus the force in the closing direction relative to fixed housing 42 is applied to movable housing 43.
When movable housing 43 is opened by hand from this closed state, movable case 35 coupled to movable housing 43 rotates, and each of the tips of movable cams 34 rides over a tip of fixed cam 32, and resiliently contacts sloped portion 32C. Now, a force in an opening direction is applied to movable member 33, and thus the force in the opening direction relative to fixed housing 42 is applied to movable housing 43.
Movable case 35 is pressed against stopper plate 38 by a counteraction of the force of spring 36 toward movable member 33. Accordingly, a friction occurs between movable case 35 and stopper plate 38 when movable housing 43 is opened and closed, as described above.
Stopper plate 38 is made by punching out a relatively hard metal sheet. On the other hand, movable case 35 is made by drawing a relatively soft metal sheet. Accordingly, movable case 35 wears and a smooth operation feeling is degraded on repeating opening and closing operations.
One prior art device related to the present invention is disclosed in Japanese Patent Unexamined Publication No. 2005-346992.